Combustor and combustion apparatus

ABSTRACT

A new combustion process wherein combustion efficiency is retained while reducing inlet air temperature to the combustor so as to obtain reduced nitrogen oxides emissions. A new combustor, and a new combination of combustion apparatus and heat utilization apparatus are also provided.

United States Patent Quigg 1 1 Feb. 11, 1975 i 1 COMBUSTOR ANDCOMBUSTION [56] References Cited APPARATUS UNITED STATES PATENTSInventor: Harold Q gg. Bartlesville, Okla 2,725,929 12/1955 Massier431/158 3,736,747 6/]973 Warren 60/39.65 [73] Assgnee' g zf gif3,814,575 6/1974 Cox et al. 431 /352 3,820,320 6/1974 Schirmer et al.431/10 x [22] Filed: Apr. 11,1974 [2]] App]. NO: 459956 PrimaryExaminer-Edward G. Favors I Related U.S. Appllcatlon Data [57] ABSTRACT[60] D1v1s1on of Ser. No. 238,318, March 27. I972, Pat.

No. 3,826,078, which is a continuation-in-part of Ser. A new CombustionProcesS Where!" Combustion No, 203,245, Dec. 15, 1971, abando ed, ciencyis retained while reducing inlet air temperature to the combustor so asto obtain reduced nitrogen 0x- 1521 US. Cl 431/215, 60/39.65, 431/352ides mis ion A ne m r, n a n c m ina- [Sl Int. Cl. F23d 11/44 tion ofcombustion apparatus and heat utilization ap- {581 Field of Search431/215, 10, ll, 352, 158; paratus are also provided.

60/39 9 39 432/222 13 Claims, 12 Drawing Figures FUEL PA ENTEUFEB] H975SHEET h 0F 4 JOm COMBUSTOR AND COMBUSTION APPARATUS This application isa division of copending application Ser. No. 238,318 filed Mar. 27,1972, now Pat. No. 3,826,078, which was a continuation-in-part of thencopending application Ser. No. 208,245, filed Dec. 15, 197], nowabandoned.

This invention relates to improved combustors, and an improvedcombination of combustion apparatus and heat utilization apparatus.

Air pollution has become a major problem in the United States and otherhighly industrialized countries of the world. Consequently, the controland/or reduction of said pollution has become the object of majorresearch and development effort by both governmental and nongovernmentalagencies. Combustion of fossil fuel is a primary source of saidpollution. It has been alleged, and there is supporting evidence, thatthe automobiles employing conventional piston-type engines burninghydrocarbon fuels are a major contributor to said pollution. Vehicleemission standards have been set by the U.S. Environmental ProtectionAgency which are sufficiently restrictive to cause automobilemanufacturers to consider employing alternate engines instead of theconventional piston engine.

The gas turbine engine is being given serious consideration as analternate engine. However, insofar as is presently known, there is nopublished information disclosing realistic and/or practical combustionprocesses or combustors which can be operated at conditions typical ofthose existing in high performance engines, and which will have emissionlevels meeting or reasonably approaching the standard set by said UnitedStates En vironmental Protection Agency. This is particularly true withrespect to nitrogen oxides emissions. Thus, there is a need for acombustion process, and a combustor of practical and/or realisticdesign, which can be operated in a manner such that the emissionstherefrom will meet said standards. Even a process and/or a combustorgiving reduced emissions approaching said standards would be a greatadvance in the art. Such a process or combustor wouldhave greatpotential value because it is possible the presently very restrictivestandards may be reduced.

In the operation of combustion processes, conservation ofthe thermalenergy produced is essential for efficiency. For example, in current gasturbine engines being proposed for automotive service, the turbineexhaust gases are heat exchanged with the inlet air to the primarycombustion some of the combustor so as to recover heat from said exhaustgases and improve overall efficiency. However, these engines will notmeet the emission standards set by said Environmental Protection Agency.

The present invention solves the above-described problems byheat-exchanging the turbine exhaust gases with another air stream to thecombustor, e.g., the dilution or quench air, instead of the primaryinlet air. The method of the invention thus provides for reducing thetemperature of the primary inlet air to the combustor. This reduces thetemperature in the combustor which results in reduced nitrogen oxidesemissions. Thus, the overall advantageous result of the inventionincludes (1 reduction of nitrogen oxide emissions from the combustorwhile (2) maintaining thermal efficiency by returning the recovered heatto the process at a point where it has no effect on nitrogen oxidesproduction. The invention also provides novel combustors, and a novelcombination of combustion apparatus and heat utilization apparatus.

According to the invention, there is provided an apparatus for producingand utilizing heat energy, comprising, in combination: an air supplyconduit; a combustion means for burning a fuel to produce hot combustiongases containing heat energy, said combustion means comprising a primarycombustion region, a secondary combustion region located downstream fromsaid primary combustion region, and a quench or dilution region locateddownstream from said secondary combustion region; a fuel inlet means forintroducing a fuel into said primary combustion region; a primary airconduit means connected to said air supply conduit and said combustionmeans at said primary combustion region for introducing a stream of aircomprising primary air into said primary combustion region; a secondaryair conduit means connected to said air supply conduit and saidcombustion means at said secondary combustion region for introducing astream of air comprising secondary air into said secondary combustionregion; a heat exchange means; a quench air conduit means connected tosaid air supply conduit, said heat exchange means, and said combustionmeans at said secondary combustion region and said quench region fordelivering a stream of air from said air supply conduit, through saidheat exchange means, and introducing heated air into at least one ofsaid secondary combustion region and said quench or dilution region ofsaid combustion means; a heat energy utilization means for utilizing aportion of said heat energy; an effluent conduit means for passing hotcombustion gases from said combustion means to said heat energyutilization means; and an exhaust conduit means connecting said heatenergy utilization means and said heat exchange means for passingexhaust hot combustion gases from said heat energy utilization means andinto heat exchange with the air from said quench air conduit means andthereby utilize an additional portion of said heat energy.

Still further according to the invention, there is provided a combustorcomprising, in combination: an outer tubular casing; a flame tubedisposed concentrically within said casing and spaced apart therefrom toform a first annular chamber between said flame tube and said casing; anair inlet means for introducing a stream of air comprising primary airinto the upstream end portion of said flame tube; a fuel inlet means forintroducing fuel into the upstream end portion of said flame tube; animperforate sleeve surrounding an upstream portion of said flame tubeand spaced apart therefrom to longitudinally enclose an upstream portionof said first annular chamber and define a second annular chamberbetween said sleeve and said outer casing; a wall member closing thedownstream end of said second annular chamber; a baffle member closingthe upstream end of said enclosed portion of said first annular chamber;at least one opening provided in the wall of said flame tube at a firststation located intermediate the upstream and downstream ends thereof; afirst conduit means extending from said second annular chamber intocommunication with said opening located at said first station foradmitting a second stream of air from said second annular chamber intothe interior of said flame tube; at least one other opening provided inthe wall of said flame tube at a second station located downstream fromsaid first station for admitting a third stream of air from said firstannular chamber into the interior of said flame tube; and a secondconduit means extending through said outer casing, said second annularchamber, said sleeve, and into communication with said enclosed portionof said first annular chamber for admitting a stream of air thereto.

FIG. 1 is a diagrammatic flow sheet illustrating methods of producingand utilizing heat energy in accordance -with the invention. I

FIG. 2 is a diagrammatic illustration of methods and apparatus inaccordance with the invention.

FIG. 3 is a view in cross section of a combustor in accordance with theinvention.

FIGS. 4, 5, 6, and 7 are views in cross section taken along the lines44, 5-5, 6-6, and 7-7, respectively, of FIG. 3.

FIG. 8 is a fragmentary perspective view of a combustor flame tubeillustrating another type of fin or extended surface which can beemployed thereon.

FIG. 9 is a partial view in cross section of another combustor inaccordance with the invention.

FIG. 10 is a front elevation view taken along the lines 110 10 of FIG.9.

FIG. 11 is a cross section view in elevation of the swirl plate of thedome or closure member in the combustor of FIG. 9.

FIG. 12 is a diagrammatic view, partially in cross section of anothercombustor in accordance with the invention.

Referring now to the drawings, wherein like reference numerals areemployed to denote like elements, the invention will be more fullyexplained. In FIG. 1 a stream of air from an air supply conduit 10 isdivided into a first stream of air in conduit 12 and a second stream ofair in conduit 14. In one embodiment, at least a portion of said firststream of air 12 is passed into combustion zone 16. A stream of fuel isintroduced into said combustion' zone via conduit 18. Said combustionzone can comprise any suitable type of combustion zone for burning amixture of fuel and air to produce hot combustiongases containing heatenergy. For example, said combustion zone can be a combustor in a gasturbine engine, a combustor in an aircraft jet engine, a combustor orother furnace employed in a boiler for generating steam, or other typesof stationary power plant, etc.

Said fuel and said first stream of air are at least partially mixed toform a combustible mixture which is burned to produce hot combustiongases containing heat energy. Said hot combustion gases are passed viaconduit 20 to heat energy utilization zone 22 so as to utilize a portionof the heat energy in said gases. Said heat energy utilization zone cancomprise any suitable method and/or means for utilizing or putting touse the heat energy contained in said hot combustion gases. For example,a turbine in a gas turbine engine wherein heat energy is converted tomechanical energy, or the heat exchange tubes in a boiler where water isconverted to steam, etc.

Said second stream of air in conduit 14 is passed through heat exchangezone 24 in heat exchange relationship with an exhaust stream in conduit26 from heat energy utilization zone 22 so as to'heat said air andthereby utilize an additional portion of said heat energy. Said heatexchange zone can comprise any suitable method and/or means foreffecting heat exchange between two separate streams of fluids, e.g.,indirect heat exchange. The heated second stream of air is passed fromsaid heat exchange zone via conduit 15 and returned to said combustionzone 16, preferably at a downstream location therein, to serve as adiluent or quench medium to lower the temperature of the effluent gasesin conduit 20 before they are passed to the heat energy utilization zone22.

In one preferred embodiment of the invention, said combustion zone 16can comprise a primary combustion region, a secondary combustion regionlocated downstream from said primary combustion region, and a quench ordilution region located downstream from said secondary combustionregion. In this and other embodiments, said first stream of air inconduit 12 is further divided into a stream comprising primary air andanother stream comprising secondary air. Said primary air is introducedinto said primary combustion region and said secondary air is introducedinto said secondary region via conduit 30. At least a portion of saidheated second stream of air-is introduced into said quench or dilutionregion via conduit 15, as before.

In another preferred embodiment of the invention, a portion of saidheated second stream of air in conduit 15 can be passed via conduit 31into conduit 30 for mixing with and increasing the temperature of thesecondary air therein. The valves in said conduits 30 and 31 can beemployed to regulate the relative proportions of the two streams of air.

FIG. 2 illustrates one embodiment of the invention wherein the effluentgases from combustor 16 are passed via conduit 20 to a turbine 25. Inturbine 25 a portion of the heat energy in said gases is converted tomechanical energy to drive shaft 28 which can be connected to anysuitable load. Exhaust gases from turbine 25 are passed via conduit 26to heat exchanger 24 and exhausted therefrom via conduit 27.

In FIG. 3 there is illustrated a combustor in accordance with theinvention, denoted generally by the reference numeral 40, whichcomprises an elongated flame tube 42. Said flame tube 42 is open at itsdownstream end, as shown, for communication with a conduit leading to aturbine or other utilization of the combustion gases. A closure or domemember, designated generally by the reference numeral 44, is providedfor closing the upstream end of said flame tube, except for the openingsin said dome member. An outer housing or casing 46 is disposedconcentrically around said flame tube 42 and spaced apart therefrom toform a first annular chamber 48 around said flame tube and said dome orclosure member 44. Said annular chamber 48 is closed at its downstreamend by any suitable means such as that illustrated. Suitable flangemembers, as illustrated, are provided at the downstream end of saidflame tube 42 and outer housing 46 for mounting same and connecting sameto a conduit leading to a turbine or other utilization of the combustiongases from the combustor. Similarly, suitable flange members 50 and 52are provided at the upstream end of said flame tube 42 and said outerhousing 46 for mounting same and connecting same to a suitable conduitmeans which leads from a compressor or other source of air. Asillustrated in the drawing, said upstream flange members comprise aportion of said outer housing or casing 46 which enclose dome member 44and forms the upstream end portion of said first annular chamber 48. Itwill be understood that outer housing or casing 46 can be extended, ifdesired, to enclose dome 44 and said upstream flanges then relocated onthe upstream end thereof. While not shown in the drawing, it will beunderstood that suitable support members are employed for supportingsaid flame tube 42 and said closure member 44 in the outer housing 46and said flange members. Said supporting members have been omitted so asto simplify the drawing.

An air inlet means is provided for introducing a swirling mass or streamof air into the upstream end portion of flame tube 42. As illustrated inFIGS. 3 and 6, said air inlet means comprises a generally cylindricalswirl chamber 54 formed in said dome member 44. The downstream end ofswirl chamber 54 is in open communication with the upstream end of flametime 42. A plurality of air conduits 56 extend from said first annularchamber 48, or other suitable source of air, into swirl chamber 54tangentially with respect to the inner wall thereof.

A fuel inlet means is provided for introducing a stream of fuel into theupstream end portion of flame tube 42. As illustrated in FIG. 3, saidfuel inlet means comprises a hollow conduit 58 for introducing a streamof fuel into the upstream end of swirl chamber 54 and axially withrespect to said swirling stream of air. Any

other suitable fuel inlet means can be employed.

A flared expansion passageway 60 is formed in the downstream end portionof dome or closure member 44. Said flared passageway flares outwardlyfrom the downstream end of swirl chamber 54 to a point on the inner wallof flame tube 42.

An imperforate sleeve 62 surrounds an upstream portion of said flametube 42. The outer wall of said sleeve can be insulated if desired andthus increase its effectiveness as a heat shield. Said sleeve 62 isspaced apart from flame tube 42 so as to longitudinally enclose anupstream portion 48 of said first annular chamber 48 and define a secondannular chamber 64 between said sleeve 62 and outer casing 46. Anannular wall member 66, secured to the inner periphery of casing 46, isprovided for closing the downstream end of said second annular chamber64. An annular baffle member 68, secured to the outer wall of flame tube42 and the inner wall of sleeve 62, is provided for closing the upstreamend of said enclosed portion 48' of first annular space 48. At least oneopening 70 is provided in the wall of flame tube 42 at a first stationlocated intermediate the ends of said flame tube. In most instances, itwill be preferred to provide a plurality of openings 70, as illustrated.A generally tubular conduit means 72 extends from said second annularchamber 64 into communication with said opening 70 for admitting asecond stream of air from said second annular chamber 64 into theinterior of flame tube 42. When a plurality of openings 70 are provided.a plurality of said tubular conduits 72 are also provided, with eachindividual conduit 72 being individually connected to an individualopening 70. The above-described structure thus provides an imperforateconduit means comprising second annular chamber 64 and tubularconduit(s) 72 for admitting a second stream of air into the interior offlame tube 42.

At least one other opening 74 is provided in the wall of flame tube 42at a second station located downstream and spaced apart from said firststation for admitting a third stream of air from first annular chamber48 into the interior of flame tube 42. In most instances, it will bepreferred to provide a plurality of openings 74 spaced around theperiphery of said flame tube, similarly as illustrated. A second conduitmeans 15 extends through said outer casing 46, said second annularchamber 64, said sleeve 62, and into communication with said enclosedportion 48 of first annular chamber 48 for admitting a stream of airthereto. If desired, said conduit 15 can communicate with thenonenclosed portion of annular chamber 48.

Preferably, the outer wall surface of flame tube 42 is provided with anextended surface in the form of fins or tabs mounted thereon in theregion surrounded by sleeve 62, and which extend into the portion 48' ofsaid first annular chamber which is enclosed by said sleeve. Asillustrated in FIGS. 3, 4, and 5, said fins or tabs 76 and 78 can bearranged in rows which extend around the periphery of the flame tube 42,and which are spaced apart longitudinally on said flame tube. The finsor tabs 76, in each row thereof, can be spaced apart circumferentiallyto provide passageways 77 therebetween. See FIG. 4. Similarly,passageways 79 can be provided between the circumferentially spacedapart fins or tabs 42. See FIG. 5. FIG. 8 illustrates another type offin which can be employed. In FIG. 8 the fins 80 extend longitudinallyof flame tube 42. Said fins 76, 78, and 80 can extend into enclosedportion 48 any desired distance.

FIG. 7 illustrates one type of structure which can be employed toprovide tubular conduits 72. A plurality of boss members 82, spacedapart circumferentially in arow around the periphery of flame tube 42,is provided downstream from the last row of fins 78. Said boss members82 have the general shape of fins 76 and 78 and passageways 83 areprovided therebetween, similarly as for passageways 77 and 79 in therows of fins 76 and 78. Said imperforate sleeve 62 extends over bossmembers 82, similarly as for fins 76 and 78, and said conduits 72 can beformed by cutting through said sleeve 62 and said boss members 80 intocommunication with openings 70 in flame tube 42. Said passageways 77, 79and 83 thus provide communication through enclosed portion 48', aroundtubular conduits 72, and into the downstream portion of first annularchamber 48.

Referring now to FIG. 9, there is illustrated the upstream portion ofanother combustor in accordance with the invention. The downstreamportion of the combustor of FIG. 9 is like the combustor of FIG. 3. Aclosure member or dome, designated generally by the reference numeral85, is mounted in the upstream end of flame tube 42 so as to close theupstream end of said flame tube except for the openings provided in saidclosure member. Said closure member can be fabricated integrally, i.e.,as one element. However, in most instances it will be preferred tofabricate said closure member in a plurality of pieces, e.g., anupstream element 86, a swirl plate 87 (see FIG. 11), and a downstreamelement or radiation shield 88. An air inlet means is provided forintroducing a swirling mass of air into swirl chamber 89 which is formedbetween swirl plate 87 and radiation shield 88, and then into theupstream end of flame tube 42. As illustrated in FIGS. 9, l0, and 11,said air inlet means comprises a plurality of air conduits 90 and 90'extending through said upstream member 86 and said swirl plate 87,respectively. A plurality of angularly disposed baffles 91, one for eachof said air conduits 90, are formed on the downstream side of said swirlplate adjacent the outlets of said air conduits.

A fuel inlet means is provided for introducing a stream of fuel into theupstream end of flame tube 42. As illustrated in FIG. 9, said fuel inletmeans comprises a fuel conduit 92 leading from a source of fuel,communicating with a passageway 93 formed in upstream element 86, whichin turn communicates with chamber 94, also formed in element 86. A spraynozzle 95 is mounted in a suitable opening in the downstream side ofsaid element 86 and is in communication with said chamber 94. Any othersuitable type of spray nozzle and fuel inlet means can be employed,including other air assist atomization nozzles. For example, it iswithin the scope of the invention to employ other nozzle types foratomizing normally liquid fuels such as nozzles wherein a stream of airis passed through the nozzle along with the fuel.

FIG. 12 is a diagrammatic illustration of another type of combustorwhich can be employed in the practice of the invention. This combustoris similar to the combustor illustrated in FIG. 3. In the combustor ofFIG. 12 the tubular conduits 72' extend transversely through annularchamber 48 and through outer casing 46. Said tubular conduits 72' canextend to the front or upstream end of the combustor, as illustrated,and be connected to the same source of air as is supplying chamber 48;or said conduits 72' can be connected to another source of air. As hereillustrated, said closure member 44' is like closure member 44 in FIG.3. However, it is within the scope of the invention to employ any othersuitable type of closure member, such as closure member 85 in FIG. 10.

In a preferred method of operating the combustor of FIG. 3, a stream ofair from a compressor or other source (not shown) is divided into afirst stream of air and a second stream of air, said first stream of airis passed, via a conduit connected to flange 52, into the upstream endof annular space 48. Said first stream of air is further divided into astream comprising primary air and a stream comprising secondary air.Said primary air is passed from annular space 48, through tangentialconduits 56, and into swirl chamber 54. Said tangential conduits imparta helical or swirling motion to the air entering said swirl chamber andexiting therefrom. This swirling motion creates a strong vortex actionresulting in a reverse circulation of hot gases within flame tube 42.

A stream of fuel, preferably prevaporized is admitted, via conduit 58,axially of said swirling stream of air. Controlled mixing of said fueland. said air occurs at the interface therebetween. The fuel and airexit from swirl chamber 54 via expansion passageway 60 wherein they areexpanded in a uniform and graduated manner, during at least a portion ofthe mixing thereof, from the volume in the region of the initial contacttherebetween to the volume of the primary combustion region, i.e., theupstream portion of flame tube 42.

Said secondary air is passed from the upstream end of annular chamber 48via second annular chamber 64, tubular conduits 72, and openings 70 intoa second region of the combustor which is located downstream from saidprimary combustion region.

The above-mentioned second stream of air. after passing through a heatexchanger such as heat exchanger 24 in FIG. I. enters the combustor viaconduit l and is passed from the upstream end ofthe enclosed portion 48'ot annular chamber 48 through the enclosed portion 48', around tubularconduits 72, into the downstream portion of annular chamber 48, and thenvia openings 74 into a third region of the combustor which is locateddownstream from said second region. Said second stream of air comprisesand can be referred to as quench or dilution air. Conduit 15 cancommunicate with enclosed portion 48', or the downstream portion offirst annular space or chamber 48, at any desired location. However, theupstream end of enclosed portion 48 is a preferred location because theair flowing over the finned wall portion of flame tube 42 serves to coolsaid wall portion and remove heat from the interior of said flame tube,and thus cause the primary combustion region to operate at a lowertemperature. This aids further in reducing nitrogen oxide emissions.

In one preferred method, the operation of the combustor in FIG. 9 issimilar to the above-described operation of the combustor of FIG. 3, andreference is made thereto. The principal difference is in the operationof closure member (FIG. 9) and closure member 44 (FIG. 3). In FIG. 9,primary air is passed through said openings and 90', strikes saidbaffles 91, and has a swirling motion imparted thereto in chamber 89. Aswirling stream of air exits from swirl chamber 89 through the openingin radiation shield 88 which surrounds nozzle 95. A stream -of liquidfuel is passed through conduit 92, passageway 93, chamber 94, and exitsfrom nozzle in a generally coneshaped discharge. Said fuel contacts saidstream of air, with said air stream assisting the action of nozzle 95 inatomizing said fuel.

The operation of the combustor illustrated in FIG. 12 is similar to thatdescribed abovefor the combustors of FIGS. 3 and 9, taking intoconsideration the type of dome or closure member employed on theupstream ends of the flame tubes. The combustor of FIG. 12 isparticularly adapted to be employed in those embodiments of theinvention wherein the stream of secondary air admitted through openings70' can have a temperature greater than the temperature of the primaryair admitted through dome or closure member 44'. When tubular conduits72' are connected to the same source of air as is supplying chamber 48,the temperature of the secondary air can be substantially the same asthe primary air. Or, the temperature of the secondary air can beincreased to be greater than the temperature of the primary air by meansof a connection between said conduits 72' and conduit 15', similarly asillustrated in FIGS. 1 and 2. When conduits 72' are connected to asource of air other than that supplying chamber 48, the temperature ofthe secondary air can be substantially the same as, or greater than, thetemperature of the primary air. Any suitable means can be employed forheating said secondary air, e.g., a connection to conduit 15', or aseparate heater or heat exchange means for heating the air passingthrough said conduits 72'.

It is within the scope of the invention to operate the combustors orcombustion zones employed in the practice of the invention under anyconditions which will give the improved results of the invention. Forexample, it is within the scope of the invention to operate saidcombustors or combustion zones at pressures within the range of fromabout I to about 40 atmospheres, or higher; at flow velocities withinthe range of from about I to about 500 feet per second, or higher; andat heat input rates within the range of from about 30 to about 1200 Btuper pound of air. Since the invention provides for reducing thetemperature of the primary inlet air to the combustor or combustionzone, to values less than those normally employed, so as to reducenitrogen oxides emissions, it is preferred that the temperature of theinlet primary air be within the range of from ambient to about 700 F.,more preferably from ambient to about 500 F. In a preferred embodimentof the invention, the temperature of the secondary air will be about thesame as said primary air. However, it is within the scope of theinvention for the temperature of the secondary air to be greater, e.g.,about 100 to 500 F., preferably about 100 to 300 F., greater than thetenperature of said primary air, e.g., when the secondary air is passedover a portion of the flame tube wall or is heated by having a portionof the heated air in conduit mixed therewith via conduit 31, see FIGS. 1and 2. The temperature of the dilution or quench air can be any suitabletemperature depending upon materials of construction in the equipmentemployed downstream from the combustor, e.g., turbine blades, and howmuch it is desired to cool the combustor effluent. Generally speaking,operating conditions in the combustors employed in the practice of theinvention will depend upon where the combustor is employed. For example,when the combustor is employed with a high pressure turbine, higherpressures and higher inlet air temperatures will be employed in thecombustor. Thus, the invention is not limited to any particularoperating conditions.

The relative volumes of the above-described primary, secondary, andquench or dilution air streams will depend upon the other operatingconditions. Generally speaking, the combined volume of said primary airand said secondary air will usually be a minor proportion of the totalair to the combustor, e.g., less than about 50 volume percent, with saidprimary air being in the range of up to about 25 volume percent and saidsecon' dary air being in the range of up to about 24 volume percent. Thevolume of said quench or dilution air will usually be a major portion ofthe total air to the combustor, e.g., more than about 50 volume percent.The relative volumes of said primary, secondary, and quench air streamscan be controlled by varying the sizes of the openings, relative to eachother, through which said streams of air are admitted to the flame tube.Any other suitable means of controlling said air volumes can beemployed, e.g., flow meters on each air stream.

The term air is employed generically herein and in the claims, forconvenience, to include air and other combustion-supporting gases.

The following examples will serve to further illustrate the invention.

EXAMPLE I A series of runs was made in a combustor typical of prior artcombustors. Said combustor basically embodied the principal features ofcombustors employed in modern aircraft turbine engines. The combustorwas a straight-through can-type combustor employing fuel atomization bya single simplex-type nozzle. The combustor liner (flame tube) wasfabricated from 2-inch pipe, with added internal deflector skirts forair film cooling of surfaces exposed to the flame. Exhaust emissionsfrom this combustor, when operated at comparable conditions forcombustion, are in general agreement with measurements presentlyavailable from several different gas turbine engines. A. commercial TypeA jet fuel was employed in these test runs. Runs were made at operatingconditions simulating idle conditions and at operating conditionssimulating maximum power conditions. Analyses for content of nitrogenoxides (reported as NO), carbon monoxide, and hydrocarbons (reported ascarbon) in the combustor exhaust gases were made at each test condition.The method for measuring nitrogen oxides was based on the Saltzmantechnique, Analytical Chemistry 26, No. 12, I954, pages l949l955. Carbonmonoxide was measured by a conventional chromatographic technique.Hydrocarbon was measured by the technique described by Lee and Wimmer,SAE Paper 680769. Each pollutant measured is reported in terms of poundsper 1000 pounds of fuel fed to the combustor. The results of these runswere as follows:

Test Conditions In another series of runs wherein the combustor wasoperated (using the same fuel) at a pressure of 450 inches of Hg. abs.,a gas velocity of I40 feet per second, and a variable heat input rate,it was found that when the air inlet temperature was increased over arange from 400 F. to about 1150 F., the nitrogen oxides emissionsincreased substantially uniformly from about 3 to about 23.5 lbs. perI000 lbs. of fuel burned.

Based on the above data, it was calculated that a combustor orcombustion zone operated in accordance with the method of the invention,at a primary air inlet temperature of about 300 F., would have nitrogenoxides emissions of about 0.6 pound per 1000 pounds of fuel at idleconditions, and about 0.9 pound per 1000 pounds of fuel at maximum powerconditions.

EXAMPLE II A series of test runs was carried out employing combustors Aand B. Combustor A was like the combustor illustrated in FIG. 3 exceptthat conduit 15 was omitted and a row of fins 76 replaced baffle 68.Combustor B was like the combustor illustrated in FIG. 9 except thatconduit 15 was omitted and a row of fins 76 replaced baffle 68.Additionally, the fins on the flame tube of combustor B were modified byplacing Vs inch bars longitudinally through each row of fins 76 and eachrow of fins 78. This provided a more linear path through enclosed area48. Design details of said combustors are set forth in Table II below.Said combustors and the design details thereof are here used forillustrative purposes only and the invention is not to be construed aslimited thereto. Any suitable combustor having any suitable dimensionscan be employed in the practice of the invention. In these runs the heatinput (fuel flow) was varied, with the air flow remaining fixed, atdifferent combinations of combustor pressure, reference velocity, andinlet air temperature. Combustor A was run using a prevaporized fuel.Combustor B was run using a liquid atomized fuel. Properties of the fuelused in both combustors are set forth in Table 1 below.

TABLE 1 Philjet A-50 AST N I DistillatiomF The method of operation wasthe same for both comlsnltizlal golfing Poinzl 254 9 bustors. Forexample, referring to E10. 3, a stream of sd flggggg i 362 air from acompressor was passed Into the upstream vol. evaporates vol. evaporateend of annular space 48 and there div ded. A portion 10 VOL evaporated387 of said air was passed as primary air via mlet conduits 50 v01,evaporated 393 56 into the primary combustion region of the combus- 60evaporated 409 vol. evaporated 424 tor. A second portion of said arr waspassed as secon- 8O VOL evaporated 442 dary air via annular chamber 64,tubular conduits 72, vol. evaporated 461 d 70 t d b i n of vol.evaporated 474 an openings in 0a secon ary corn u 10H reg o 15 End Point496 the combustor. A thlrd portion of said air was passed Residue, vol.8.8 I Loss, vol. via enclosed annular chamber 48 and the downstreamGravity, degrees AP] 466 portion of annular chamber 48, and openings 74into Density, |bS/ga| 6,615 the quench region of the combustor. Likeflows were Heal of Combustion, net, Btu/lb. 18,670

FIG 9 U Hydrogen Content, wt. 1 -2 used in the combustor Illustrated insing sar 20 Smoke Pom, mm 272 flows, each of said combustors wasoperated at the test Sulfur, wt. Zo 1 8.80! points or conditions setforth in Table 11] below. Analy- 'E ses for emissions content In thecombustor exhaust Paraffms 52.8 gases were carried out as in Example 1.Emissions data g g 3:? for said test runs. mean values from duplicateruns at 25 Ar mati s 12,6 Formula (calculated) n zz) each testcondition, are set forth in Tables 1V and V be Swichiometric Fuel/AirRatio III/lb O 676 low.

TABLE I1 COMBUSTOR DESIGN Combustor Number Variable A B Closure MemberAir lnlet Diameter, in. 0.875 0.625 lnlet Type Tangent Swirl HoleDiameter, in. 0.188 0.250 Number of Holes 6 6 Total Hole Area, sq. in.0.166 0.295 Total Combustor Hole Area 3.213 5.571 Fuel Nozzle TypeSimplex Spray Angle, deg. 45 Fuel Tube Diameter, in. 0.250 Flame Tube1st Station Hole Diameter, in. 5/16 X 1* 5/16 X 1* Total Number of Holes8 8 Total Hole Area, sq. in. 2.500 2.500 Total Combustor Hole Area48.393 47.214 2nd Station Hole Diameter, in. 5/16 X 1* 5/16 X 1* TotalNumber of Holes 8 8 Total Hole Area, sq. in. 2.500 2.500 Total CombustorHole Area 48.393- 47.214 Combustor Cross-Sect. Area, sq. in. 3.355 3.355Total Combustor Hole sq. in. 5.166 5.295 Cross-Sectional Area 153.933157.777 Combustor Inside Diameter, in. 2.067 2.067 Primary Zone Length,in. 7.375 7375 Volume, cu. in. 24.748 24.748 Combustor Length, in.18.437 18.437 Volume, cu. in. 61.867 61.867

Holes are 5/16" diameter at ends; slots are 1" long.

TABLE I11 TEST CONDlTlONS COMBUSTORS A and B Primary Cold Flow Heat Testlnlet Air Combustor Reference lnput, Air Fuel Condition Temperature,Pressure, Velocity, Btu/1b. Flow, Flow, Number F. in. Hg. abs. ft./sec.Air lbJsec 1b./hr.

1 1100 250 75 0.545 7.9 2 do. do. do. 110 do. 11.6 3 do. do. do. do.15.8 4 do. do. do do. 19.4 5 do. do. do. 225 do. 23.6 6 do. do. do. 260do. 27.3 7 do. do. do. 300 do. 31.5 8 900 110 250 75 0.625 9.0

TABLE lllCnlinued TEST CONDITIONS COMBUSTORS A and B Primary Cold FlowHeat '1 051 lnlct Air Combustor Reference Input, Air Fuel ConditionTemperature, Pressure, Velocity, Btu/1b. Flow, Flow. Number F. in. Hg.abs. ftjsec. Air 1b./sec. 1b./hr

9 do. do. do. 110 do. 13.3 10 do. do. do. 150 do. 181 1 1 do. do. do.185 do. 223 12 1 do. do. do. 225 do. 27.1 13 do do do. 260 do 31.3 14 dodo do. 300 do 362 15 700 110 250 75 0 733 10.0 16 do do do. 110 do 15.517 do do do. 150 do 21.2 18 do do do. 185 do 26.1 19 do do do. 225 do31.8 20 do do do. 260 do 36.7 21 do do do. 300 do 424 22 500 110 250 750 885 12.8 23 do do do. 1 10 do 18.8 24 do do do. 150 do 25.6 do do do.185 do 31.6 26 do do do. 225 do 38.4 7 do do do. 260 do 44.4 28 do dodo. 300 do 51.2

TABLE IV SUMMARY OF EMISSION DATA FROM COMBUSTOR A Test Primary ZoneCondition Residence E uivalence Emissions, lbs/1000 lbs. fuel NumberTime, msec atio,d NO, (as NO) CO HC (as C) 1 76.6 1.85 19.8 2 0.6 2 do.2.72 9.4 28 0.3 3 do. 3.71 3.2 26 0.2 4 do. 4.55 3.0 14 0.2 5 do. 5.542.4 0.2 6 do. 6.40 2.2 9 0.1 7 do. 7.40 2.6 3 0.2 8 76.6 1.84 9.5 51 0.59 do. 2.72 4.1 35 1.2 10 do. 3.71 1.6 54 0.8 11 do. 4.56 1.0 46 0.2 12do. 5.54 0.6 24 0.2 13 do. 6.40 0.9 17 0.1 14 do. 7.40 1.2 2 0.2 15 o76.6 1.85 5.7 0 0.5 16 do. 2.70 3.8 94 0.3 17 do. 3.70 1.4 108 0.2 18do. 4.55 0.9 80 0.2 19 do. 5.54 0.7 30 0.2 20 do. 6 .40 0.8 20 0.1 21do. 7.40 1.4 40 0.7 22 76.6 1.85 4.1 6 1.0 23 do. 2.72 3.5 116 0.9 24do. 3.70 1.1 134 0.2 25 I do, 4 56 0.9 109 0.4 26 do. 5 54 0.8 72 0.4 27do. 6 0.5 86 4.2 28 do. 7 40 0.8 101 8.2

TABLE V SUMMARY OF EMISSION DATA FROM COMBUSTOR B Test Primary ZoneCondition Residence Equivalence Emissions, lbs./ 1000 lbs. fuel NumberTime, msec Ratio, 4: NO, (as NO) CO HC (as C) 1 44.2 1.07 18.8 0 0.5 2do. 1.57 7.0 32 0.3 3 do. 2.14 5.7 14 0.4 4 do. 2.63 2.1 6 0.1 5 do.3.19 1.9 2 0.1 6 do. 370 2.2 2 0.2 7 do. 426 2.0 1 0,0 8 44.2 1.06 9.4 40.5 1 do. 1.57 3.9 77 0.3 10 do. 2.14 1.4 53 0.1 11 do. 2.03 L4 22 (1.312 do. 320 1.5 7 0.2 13 do. 370 1.6 2 0.2 14 do. 4.27 1.8 0 0.1 15 44.21.07 6.7 7 0.5 16 do. 1.56 2.8 112 0.3 17 do. 2.13 1.6 122 0.2

TABLE V- Continued SUMMARY OF EMISSION DATA FROM COMBUSTOR B TestPrimary Zone Condition Residence Equivalence Emissions, lbs/1000 lbs.fuel Number Time, msec Ratio, ()5 NO, (as NO) CO HC (as C) l8 do. 2.63L1 76 0.2 19 do. 320 1.0 28 0.2 20 do. 3.69 1.3 l0 0.] 21 do. 4.26 1.2 40.0 22 44.2 1.07 3.1 10 1.4 23 do. 1.57 l.4 l9l 0.5 24 do. 2.13 1.1 2320.3 25 do. 2.63 1.2 153 0.2 26 do. 3.20 0.9 107 0.4 27 do. 3.70 1.0 500.6 28 do. 4.26 1.0 26 0.4

The data in the above Tables IV and V show that decreasing thetemperature of the inlet air to the primary combustion zone decreasesthe NO, emissions. The temperature of the inlet air to the second zoneof the combustor (inlet at openings 70) was not measured butapproximated the temperature of the primary air. Thus, the data alsoshow that CO emissions increase with decreasing inlet air temperaturesto the secondary combustion zone, and decrease with increasing inlet airtemperatures to said secondary combustion zone.

The data from the above runs thus illustrate the advantages of operatinga combustor and heat energy utilization system in accordance with theinvention. By heat exchanging an exhaust gas stream from the heat energyutilization zone (such as turbine exhaust gases) with one or more otherair streams to the combustor such as the quench air (and also heatingthe secondary air if desired). instead of the primary air, a combustorcan be operated with a low primary air inlet temperature, a controlledsecondary air inlet temperature which can be the same as or greater thanthe temperature of the inlet primary air, and a heated quench air streamwhich can have a greater temperature than either said primary air orsaid secondary air. The method of the invention thus provides for a lowprimary inlet air temperature to give low NO, emissions values, acontrolled secondary air inlet temperature to give desired CO emissionsvalues, and a heated quench inlet air to conserve heat energy andincrease the overall efficiency of the system.

In general, said data also show that NO, emissions decrease withincreasing equivalence ratio in the primary combustion zone (increasingfuel-rich mixture), and tend to plateau at low levels with an increasein heat input. Said equivalence ratios were calculated from the percentTotal Combustor Hole Area for the air inlet conduits to the primarycombustion zone.

The data set forth in the above Tables IV and V show that combustors canbe operated in accordance with the invention to give low N0 low CO, andlow HC emissions when using either a prevaporized fuel or an atomizedliquid fuel. Said data also show that the various operating variables orparameters are interrelated. Thus. a change in one variable or parametermay make it desirable to adjust one or more of the other operatingvariables or parameters in order to obtain desirable results withrespect to all three pollutants NO, CO, and HC (hydrocarbons).

In one presently preferred method of the invention, the primarycombustion zone is preferably operated fuel-rich with respect to theprimary air admitted thereto. Thus, the equivalence ratio in the primarycombustion zone is preferably greater than stoichiometric. In thismethod of operation, the second zone (secondary combustion zone) of thecombustor is preferably operated fuel-lean with respect to any unburnedfuel and air entering said second zone from said primary zone, and anyadditional air admitted to saidsec combustion zone be operated fuel-richas described, it

is within the scope of the invention to operate the primary combustionzone fuel-lean. Thus, it is within the scope of the invention to operatethe primary combustion zone with any equivalence ratio which will givethe improved results of the invention.

For example, in the practice of the invention as carried out in lowcompression ratio combustors, e.g., compression ratios up to about 5,the equivalence ratio in the primary combustion zone can have anyvaluesuch that the NO, emissions value in the exhaust gases from thecombustor is not greater than about 5 pounds, preferably not greaterthan about 3.5 pounds, per 1000 pounds of fuel burned in said combustor.Preferably, said equivalence ratio will be at least 1.5, more preferablyat least 3.5, depending upon the other operating variables orparameters, e.g., temperature of the inlet air to the primary combustionzone.

It will be understood that said NO, emission values referred to in thepreceding paragraph can be greater than the values there given whenoperating high performance combustors. For example, combustors such asthe intermediate compression ratio combustors having a compression-ratioof about 5 to 15 atmospheres and the high compression ratio combustorshaving a compression ratio of about 15 to about 40 atmospheres used injet aircraft and other high performance engines. The NO, emissions fromsuch high performance or high compression ratio combustors willnaturally be higher than the NO emissions from low compression ratiocombustors. Thus, greatly improved results in reducing NO emissions froma high'performance combustor can be obtained without necessarilyreducing said NO, emissions to the same levels as would be obtained froma low performance combustor.

As used herein and in the claims, unless otherwise specified, the termequivalence ratio for a particular zone is defined as the ratio of thefuel flow (fuel available) to the fuel required for stoichiometriccombustion with the air available. Stated another way, said equivalenceratio is the ratio of the actual fuel-air mixture to the stoichiometricfuel-air mixture. For example, an equivalence ratio of 2 means thefuel-air mixture in the zone is fuel-rich and contains twice as muchfuel as a stoichiometric mixture.

The data in the above examples show that the temperature of the inletair to the primary combustion zone can be an important operatingvariable or parameter in the practice of the invention. As stated above,the invention is not limited to any particular range or value EmissionLevel Criteria Pollutant EPAGas Turbine Engine Goal Nitrogen OxidesCarbon Monoxide Hydrocarbons Particulates Vehicle Standard grams/milelbs/1,000 ")5. fuel burned 0.40 (as NO 0.9 3.4 11.8 0.41 (as hexane) 1.2(as carbon) 0.03 0.1

for said inlet air temperature. It is within the scope of the inventionto use any primary air inlet temperature which will give the improvedresults of the invention, for example, from ambient or atmospherictemperatures or lower to about 1500 F. or higher. However, consideringpresently available practical materials of construction, about 1200 F.to about 1500 F. is a practical upper limit for said primary air inlettemperature in most instances. Considering other practical aspects suchas not having to cool the compressor discharge stream, about 200 to 400F. is a practical lower limit for said primary air inlet temperature inmany instances. However. it is emphasized that primary air inlettemperatures lower than 200 F. can be used, e.g., in low compressionratio combustors.

The data in the above examples also show that the temperature of the airadmitted to the second zone of the combustor (secondary combustion air)can be an important operating variable or parameter. particularly whenthe lower primary air inlet temperatures are used, and it is desired toobtain low CO emission values as well as low NO, emission values. Saiddata show that both low N0 emission values and low CO emission valuescan be obtained when the temperature of the inlet air to both theprimary combustion zone and the second zone of the combustor are atleast about 900 F. As the temperature of the inlet air to said zonesdecreases, increasingly improved (lower) values for NQ emissions areobtained, but it becomes more difficult to obtain desirably low COemission values. It is preferred that the temperature of the inlet airto the primary combustion zone not be greater than about 700 F. Thus, insome embodiments of the invention, it is preferred that the temperatureof the secondary air admitted to the second zone of the combustor begreater than the temperature of the primary air admitted to the primarycombustion zone. For example, depending upon the temperature of theinlet air to the primary combustion zone. it is preferred that thetemperature, of the inlet secondary air be in the range of from about100 to about 500 F. greater than the temperature of said inlet primaryair.

As a guide to those skilled in the art, but not to be construed asnecessarily limiting on the invention. the presently preferred operatingranges for other variables or parameters are: heat input. from 30 to 500Btu per lb. of total air to the combustor; combustor pressure,

The data set forth in the above examples show that the invention can bepracticed to give pollutant emission levels meeting the above standardsor goals. However, the invention is not limited to meeting saidstandards or goals. Many persons skilled in the art consider saidstandards or goals to be unduly restrictive. lt is possible that saidstandards or goals may be relaxed. Thus, a combustor, and/or a method ofoperating a combustor, to obtain reduced levels of pollutant emissionsapproaching said standards or goals has great potential value. While itis not to be considered as limiting on the invention, it is believedthat practical maximums for low compression ratio gas turbine enginegoals would be in the order of, in lbs. per 1000 lbs. of fuel burnedN(),,-, S; 25; and hydrocarbons, 2.

Thusfin the practice of the invention, while it is desirable to reducethe nitrogen oxides emissions from the combustors or combustion zonesemployed therein to values of not more than about 2.5, preferably notmore than about 1.8, pounds per 1000 pounds of fuel burned at idleconditions; and not more than about 5, preferably not more than about3.5, pounds per 1000 pounds of fuel burned at maximum power conditions,the invention is not limited to said values.

Thus, while certain embodiments of the invention have been described forillustrative purposes, the invention is not limited thereto. Variousother modifications or embodiments of the invention will be apparent tothose skilled in the art in view of .this disclosure. Such modificationsor embodiments are within the spirit and scope of the disclosure.

I claim:

1. An apparatus for producing and utilizing heat energy, comprising, incombination:

an air supply conduit;

a combustion means for burning a fuel to produce hot combustion gasescontaining heat energy,said combustion means comprising a primarycombustion region, a secondary combustion region located downstream fromsaid primary combustion region, and a quench or dilution region locateddownstream from said secondary combustion region;

a fuel inlet means for introducing a fuel into said primary combustionregion;

a primary air conduit means connected to said air supply conduit andsaid combustion means at said primary combustion region for introducinga stream of air compressing primary air into said primary combustionregion;

a secondary air conduit means connected to said air supply conduit andsaid combustion means at said secondary combustion region forintroducing a stream of air comprising secondary air into said secondarycombustion region;

a heat exchange means;

a quench air conduit means connected to said air supply conduit, saidheat exchange means, and said combustion means at said secondarycombustion region and said quench region for delivering a stream of airfrom said air supply conduit, through said heat exchange means, andintroducing heated air into at least one of said secondary combustionregion and said quench or dilution region of said combustion means;

a heat energy utilization means for utilizing a portion of said heatenergy;

an effluent conduit means for passing hot combustion gases from saidcombustion means to said heat energy utilization means, and

an exhaust conduit means connecting said heat energy utilization meansand said heat exchange means for passing exhaust hot combustion gasesfrom said heat energy utilization means and into heat exchange with theair from said quench air conduit means and thereby utilize an additionalportion of said heat energy.

2. An apparatus according to claim 1 wherein:

a first valve means is disposed in said secondary air conduit means forregulating the amount of air flow therethrough to said secondarycombustion region; and

a second valve means is disposed in said quench air conduit means forregulating the amount of said heated air flow to said secondarycombustion region.

3. An apparatus according to claim 1 wherein:

said combustion means comprises an elongated flame tube, with saidprimary combustion region comprising the upstream end portion of theinterior of said flame tube, said quench or dilution region comprisingthe. downstream end portion of the interior of said flame tube, and saidsecondary combustion region comprising an intermediate portion of theinterior of said flame tube;

at least one opening is provided in the wall of said flame tube at afirst station located in said secondary combustion region;

said secondary air conduit means and said quench air conduit means areeach in communication with a first conduit means which is incommunication with said first station opening for maintaining a secondstream of air comprising at least one of secondary air from saidsecondary air conduit means and heated air from said quench air conduitmeans separate from said primary air and admitting said second stream ofair into the interior of said flame tube;

at least one other opening is provided in the wall of said flame tube ata second station located in said .quench region; and

said quench air conduit means is also in communication with a secondconduit means which surrounds at least a portion of said flame tube andis in communication with said second station opening for maintaining athird stream of air comprising quench air separate from said primary airand said second stream of air and flowing said third stream of air in adownstream direction over and in heat exchange with the outer wall ofsaid flame tube and then admit said third stream of air into theinterior of said flame tube.

4. An apparatus according to claim 3 wherein:

a first valve means is disposed in said secondary air conduit means forregulating the amount of air flow therethrough to said first conduitmeans; and

a second valve means is disposed in said quench air conduit means forregulating the amount of said heated air flow therefrom and into saidfirst conduit means.

5. An apparatus according to claim 4 wherein heat exchange fins aremounted on the outer wall surface of said flame tube in at least aportion of the region surrounded by said second conduit means.

an imperforate sleeve surrounds an upstream portion of said flame tubeand is spaced apart therefrom to longitudinally enclose an upstreamportion of said first annular chamber and form a second annular chamberbetween said sleeve and said outer casing, with said second annularchamber surrounding said first annular chamber;

at least one opening is provided in the wall of said flame tube at afirst station located in said secondary combustion region;

a tubular conduit means extends between each said first station openingand said second annular chamber for providing communicationtherebetween;

said secondary air conduit means and said quench air conduit means areeach in communication with said second annular chamber which is incommunication with said first station opening via said tubular conduitmeans for maintaining a second stream of air comprising at least one ofsecondary air from said secondary air conduit means and heated air fromsaid quench air conduit means separate from said primary air andadmitting said second stream of air into the interior of said flametube;

at least one other opening is provided in the wall of said flame tube ata second station located in said quench region; and

said quench air conduit means is also in communica- -tion with saidfirst annular chamber which is in communication with said second stationopening for admitting a third stream of air comprising quench air,maintained separate from said primary air and said second stream of air,into the interior of said flame tube.

7. An apparatus according to claim 6 wherein:

a first valve means is disposed in said secondary air conduit means forregulating the amount of air flow therethrough to said second annularchamber; and

a second valve means is disposed in said quench air conduit means forregulating the amount of said heated air flow therefrom and into saidsecond annular air chamber.

8. An apparatus according to claim 6 wherein heat exchange fins aremounted on the outer wall surface of said flame tube in at least aportion of the region surrounded by said imperforate sleeve and extendinto said enclosed portion of said first annular chamber.

9. A combustor comprising, in combination:

an outer tubular casing;

a flame tube disposed concentrically within said casing and spaced aparttherefrom to form a first annular chamber between said flame tube andsaid casing;

an air inlet means for introducing a stream of air comprising primaryair into the upstream end portion of said flame tube;

a fuel inlet means for introducing fuel into the up stream end portionof said flame tube;

an imperforate sleeve surrounding an upstream portion of said flame tubeand spaced apart therefrom to longitudinally enclose an upstream portionof said first annular chamber and define a second annular chamberbetween said sleeve and said outer casing;

a wall member closing the downstream end of said second annular chamber;

a baffle member closing the upstream end of said enclosed portion ofsaid first annular chamber;

at least one opening provided in the wall of said flame tube at a firststation located intermediate the upstream and downstream ends thereof;

a first conduit means extending from said second annular chamber intocommunication with said opening located at said first station foradmitting a second stream of air from said second annular cham ber intothe interior of said flame tube;

at least one other opening provided in the wall of said flame tube at asecond station located downstream from said first station for admittinga third stream of air from said first annular chamber into the interiorof said flame tube; and

a second conduit means extending through said outer casing, said secondannular chamber, said sleeve, and into communication with said enclosedportion of said first annular chamber for admitting a stream of airthereto.

10. A combustor according to claim 9 wherein heat exchange fins aremounted on the outer wall surface of said flame tube, in the regionsurrounded by said sleeve, and extend into the portion of said firstannular chamber enclosed by said sleeve.

11. A combustor according to claim 9 wherein:

a dome member is mounted in the upstream end of said flame tube; and

said air inlet means comprises a generally cylindrical swirl chamberformed in said dome member, the downstream end of said swirl chamberbeing in open communication with the upstream end portion of said flametube, and conduit means for introducing a stream of air into said swirlchamber tangentially with respect to the inner wall thereof.

12. A combustor according to claim 11 wherein said fuel inlet meanscomprises conduit means for introducing said fuel into the upstream endof said swirl chamber and axially with respect to said swirling streamof air.

13. A combustor according to claim 12 wherein the downstream end portionof said dome member comprises an expansion passageway which flaresoutwardly from the downstream end of said swirl chamber to the innerwall of said flame tube.

1. An apparatus for producing and utilizing heat energy, comprising, incombination: an air supply conduit; a combustion means for burning afuel to produce hot combustion gases containing heat energy, saidcombustion means comprising a primary combustion region, a secondarycombustion region located downstream from said primary combustionregion, and a quench or dilution region located downstream from saidsecondary combustion region; a fuel inlet means for introducing a fuelinto said primary combustion region; a primary air conduit meansconnected to said air supply conduit and said combustion means at saidprimary combustion region for intRoducing a stream of air compressingprimary air into said primary combustion region; a secondary air conduitmeans connected to said air supply conduit and said combustion means atsaid secondary combustion region for introducing a stream of aircomprising secondary air into said secondary combustion region; a heatexchange means; a quench air conduit means connected to said air supplyconduit, said heat exchange means, and said combustion means at saidsecondary combustion region and said quench region for delivering astream of air from said air supply conduit, through said heat exchangemeans, and introducing heated air into at least one of said secondarycombustion region and said quench or dilution region of said combustionmeans; a heat energy utilization means for utilizing a portion of saidheat energy; an effluent conduit means for passing hot combustion gasesfrom said combustion means to said heat energy utilization means, and anexhaust conduit means connecting said heat energy utilization means andsaid heat exchange means for passing exhaust hot combustion gases fromsaid heat energy utilization means and into heat exchange with the airfrom said quench air conduit means and thereby utilize an additionalportion of said heat energy.
 2. An apparatus according to claim 1wherein: a first valve means is disposed in said secondary air conduitmeans for regulating the amount of air flow therethrough to saidsecondary combustion region; and a second valve means is disposed insaid quench air conduit means for regulating the amount of said heatedair flow to said secondary combustion region.
 3. An apparatus accordingto claim 1 wherein: said combustion means comprises an elongated flametube, with said primary combustion region comprising the upstream endportion of the interior of said flame tube, said quench or dilutionregion comprising the downstream end portion of the interior of saidflame tube, and said secondary combustion region comprising anintermediate portion of the interior of said flame tube; at least oneopening is provided in the wall of said flame tube at a first stationlocated in said secondary combustion region; said secondary air conduitmeans and said quench air conduit means are each in communication with afirst conduit means which is in communication with said first stationopening for maintaining a second stream of air comprising at least oneof secondary air from said secondary air conduit means and heated airfrom said quench air conduit means separate from said primary air andadmitting said second stream of air into the interior of said flametube; at least one other opening is provided in the wall of said flametube at a second station located in said quench region; and said quenchair conduit means is also in communication with a second conduit meanswhich surrounds at least a portion of said flame tube and is incommunication with said second station opening for maintaining a thirdstream of air comprising quench air separate from said primary air andsaid second stream of air and flowing said third stream of air in adownstream direction over and in heat exchange with the outer wall ofsaid flame tube and then admit said third stream of air into theinterior of said flame tube.
 4. An apparatus according to claim 3wherein: a first valve means is disposed in said secondary air conduitmeans for regulating the amount of air flow therethrough to said firstconduit means; and a second valve means is disposed in said quench airconduit means for regulating the amount of said heated air flowtherefrom and into said first conduit means.
 5. An apparatus accordingto claim 4 wherein heat exchange fins are mounted on the outer wallsurface of said flame tube in at least a portion of the regionsurrounded by said second conduit means.
 6. An apparatus according toclaim 1 wherein: said combustion means comprises an elongated flame tubedisposed within an outer casing and spaced apart therefrom to form afirst annular chamber; said primary combustion region comprises theupstream end portion of the interior of said flame tube, said quench ordilution region comprises the downstream end portion of the interior ofsaid flame tube, and said secondary combustion region comprises anintermediate portion of the interior of said flame tube; an imperforatesleeve surrounds an upstream portion of said flame tube and is spacedapart therefrom to longitudinally enclose an upstream portion of saidfirst annular chamber and form a second annular chamber between saidsleeve and said outer casing, with said second annular chambersurrounding said first annular chamber; at least one opening is providedin the wall of said flame tube at a first station located in saidsecondary combustion region; a tubular conduit means extends betweeneach said first station opening and said second annular chamber forproviding communication therebetween; said secondary air conduit meansand said quench air conduit means are each in communication with saidsecond annular chamber which is in communication with said first stationopening via said tubular conduit means for maintaining a second streamof air comprising at least one of secondary air from said secondary airconduit means and heated air from said quench air conduit means separatefrom said primary air and admitting said second stream of air into theinterior of said flame tube; at least one other opening is provided inthe wall of said flame tube at a second station located in said quenchregion; and said quench air conduit means is also in communication withsaid first annular chamber which is in communication with said secondstation opening for admitting a third stream of air comprising quenchair, maintained separate from said primary air and said second stream ofair, into the interior of said flame tube.
 7. An apparatus according toclaim 6 wherein: a first valve means is disposed in said secondary airconduit means for regulating the amount of air flow therethrough to saidsecond annular chamber; and a second valve means is disposed in saidquench air conduit means for regulating the amount of said heated airflow therefrom and into said second annular air chamber.
 8. An apparatusaccording to claim 6 wherein heat exchange fins are mounted on the outerwall surface of said flame tube in at least a portion of the regionsurrounded by said imperforate sleeve and extend into said enclosedportion of said first annular chamber.
 9. A combustor comprising, incombination: an outer tubular casing; a flame tube disposedconcentrically within said casing and spaced apart therefrom to form afirst annular chamber between said flame tube and said casing; an airinlet means for introducing a stream of air comprising primary air intothe upstream end portion of said flame tube; a fuel inlet means forintroducing fuel into the upstream end portion of said flame tube; animperforate sleeve surrounding an upstream portion of said flame tubeand spaced apart therefrom to longitudinally enclose an upstream portionof said first annular chamber and define a second annular chamberbetween said sleeve and said outer casing; a wall member closing thedownstream end of said second annular chamber; a baffle member closingthe upstream end of said enclosed portion of said first annular chamber;at least one opening provided in the wall of said flame tube at a firststation located intermediate the upstream and downstream ends thereof; afirst conduit means extending from said second annular chamber intocommunication with said opening located at said first station foradmitting a second stream of air from said second annular chamber intothe interior of said flame tube; at least one other opening provided inthe wall of said flame tube at a second station located downstream fromsaid first station for admitting a thiRd stream of air from said firstannular chamber into the interior of said flame tube; and a secondconduit means extending through said outer casing, said second annularchamber, said sleeve, and into communication with said enclosed portionof said first annular chamber for admitting a stream of air thereto. 10.A combustor according to claim 9 wherein heat exchange fins are mountedon the outer wall surface of said flame tube, in the region surroundedby said sleeve, and extend into the portion of said first annularchamber enclosed by said sleeve.
 11. A combustor according to claim 9wherein: a dome member is mounted in the upstream end of said flametube; and said air inlet means comprises a generally cylindrical swirlchamber formed in said dome member, the downstream end of said swirlchamber being in open communication with the upstream end portion ofsaid flame tube, and conduit means for introducing a stream of air intosaid swirl chamber tangentially with respect to the inner wall thereof.12. A combustor according to claim 11 wherein said fuel inlet meanscomprises conduit means for introducing said fuel into the upstream endof said swirl chamber and axially with respect to said swirling streamof air.
 13. A combustor according to claim 12 wherein the downstream endportion of said dome member comprises an expansion passageway whichflares outwardly from the downstream end of said swirl chamber to theinner wall of said flame tube.